The First Example of Molecularly Imprinted Nanogels with Aldolase Type I Activity

Abstract

The molecular-imprinting approach was used to obtain a nanogel preparation capable of catalysing the cross-aldol reaction between 4-nitrobenzaldehyde and acetone. A polymerisable proline derivative was used as the functional monomer to mimic the enamine-based mechanism of aldolase type I enzymes. The diketone template used to create the cavity was designed to imitate the intermediate of the aldol reaction and was bound to the functional monomer using a reversible covalent interaction prior to polymerisation. By using a high-dilution polymerisation method, soluble imprinted nanogels were prepared with dimensions similar to those of an enzyme and with the advantage of solubility and flexibility previously unattainable with monolithic polymers. Following template removal and estimation of active-site concentrations, the kinetic characterisation of both imprinted and non-imprinted nanogels was carried out with catalyst concentrations between 0.7 and 3.5 mol %. Imprinted nanogel AS147 was found to have a k(cat) value of 0.25 x 10(-2) min(-1), the highest value ever achieved with imprinted polymers catalysing C--C bond formation. Comparison of the catalytic constants for both imprinted nanogel AS147 and non-imprinted nanogel AS133 gave a ratio of k(cat 147)/k(cat 133)=18.8, which is indicative of good imprinting efficiency and highlights the significance of the template during the imprinting process. This work represents a significant demonstration of the superiority of nanogels, when the molecular-imprinting approach is used, over "bulk" polymers for the generation of catalysts.

pH‐Sensitive Water‐Soluble Nanospheric Imprinted Hydrogels Prepared as Horseradish Peroxidase Mimetic Enzymes

“…The catalytic efficiency of the imprinted catalyst can be estimated by the ratio of the values of V max and K m , [25,26] which Figure 3. The hydrodynamic particle size of imprinted microgels measured by dynamic light scattering.…”

Molecular Imprinting

“…An important development is the systematic decrease of particle size, resulting in nanogels with sizes in the lower nanometre range [10], which seems to convey to MIP's properties closer to those of biological antibodies, such as a quasi solubility, very few, or even one, binding site per particle, and a more homogeneous affinity distribution, which can be even further improved by fractioning the particles by affinity chromatography [11]. Resmini and colleagues [12] have shown that these particles, when imprinted with a transition state analogue, can be efficient enzyme mimics. Others have worked on improving the compatibility of MIPs with aqueous solvents, by using monomers that interact more strongly with the molecular template [13].…”

Tuning Molecular Recognition in Water‐Soluble Nanogels with Enzyme‐Like Activity for the Kemp Elimination

“…The application of the imprinting technique to cross-linked yet flexible polymeric matrices, [4] such as the microgels, [5][6][7][8] led to the first report by our group of imprinted microgels with hydrolase activity, [9][10] which represented an important advance in the field of enzyme mimics. Recently Resmini et al reported the first example of imprinted nanogels with aldolase type I activity, [11] demonstrating the feasibility of applying the imprinting approach to energetically more challenging reactions. In both cases, the template-monomer complex was based on strong ionic bonds or reversible covalent interactions.…”